KDE has announced the release of Plasma Active One, which is a KDE 4.x style interface and API designed for touch devices. The Plasma Active Team states that "Plasma Active is innovative technology for an intelligent user experience. It is intended for all types of tablets, smartphones and touch computing devices such as set-top boxes, smart TVs, home automation, in-vehicle infotainment".

NVidia, TI, and Qualcomm each do their own thing in their little corner, and if it has not changed since the last time I checked, the only resource which they publicly provide to OS developers are binary Android drivers.

True, re-flashing and some of the hardware drivers are the issues.

The hardest issue is the lack of accelerated graphics drivers, as its the key element and no easy task to develop. As for the rest of the peripherals in the SoCs, it's far less complex is somewhat better documented and there are lots of code for similar hardware that can be adapted.

The second mayor issue is the re-flashing, the complexity and the risk of bricking are a serious roadblock for most.

As for the SoC vendors, currently the best bet is to find something with a touch screen and a TI SoC(Anyone know of such a tablet?). On such a device, the issues would mainly be about the re-flashing. Since most of the drivers already have quite mature solutions, thanks to the Beagle and Panda boards.